Trace H2O2-triggered Fenton-like reaction by secondary coordination sphere in iron-based metal-organic frameworks

Minimizing H2O2 consumption for efficient water decontamination is a crucial objective of Fenton-like reaction. However, the limited H2O2 activation and hydroxyl radicals (·OH) utilization efficiency are still two obstacles, mainly caused by high O-O bond energy barrier and short-lived free·OH generation. Here, we show an iron-based metal-organic frameworks with pyridine N secondary coordination sphere, i.e., N/MIL-53(Fe), whereas secondary coordination sphere has a strong interaction with the key *OH intermediates, thereby decreasing O-O homolytic cleavage barrier and promoting in-situ generation of long-lived adsorbed ·OH. Therefore, N/MIL-53(Fe) exhibits a H2O2 conversion efficiency up to about 90%, with adsorbed ·OH accounting for over 90% of the total. Meanwhile, N/MIL-53(Fe) achieves high activity for bisphenol A, tetracycline, phenol, p-chlorophenol and ciprofloxacin degradation (98% within 5 min) under trace H2O2 (0.5 mM), with H2O2 consumption equivalent to only 3% ~ 10% of reported Fenton-like catalyst. This study provides an efficient pathway for low-consumption water decontamination. Fenton-like water treatment is limited by inefficient hydrogen peroxide activation and short-lived reactive radicals. Adding nearby nitrogen sites to iron metal-organic frameworks boosts peroxide use and traps radicals, enabling rapid pollutant removal.